Manufacturing method of stretched film

Abstract

To provide a manufacturing method which can suppress generation of unevenness in a film and can manufacture a stretched film having desired characteristics, even if a resin film is formed using a recycled material.SOLUTION: A method for manufacturing a stretched film includes: a step of forming a resin film from a virgin material and a recycled material, forming width direction both ends of the resin film from the recycled material, and forming a body part positioned therebetween from the virgin material; a step of cutting the resin film and separating it into a first end film and a formation film; and a step of stretching the formation film. The melt viscosity of the virgin material and the recycled material satisfies the following expression (1). In the expression (1), A represents the melt viscosity of the virgin material, and C represents the melt viscosity of the recycled material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a stretched film. [Background technology]

[0002] Stretched films, which are widely used in various industrial products, are produced by stretching a resin film. For example, a method for producing a stretched film has been proposed in which a long resin film is stretched in a direction intersecting the long direction while both ends in the width direction of the film are held by clips (see, for example, Patent Document 1). In recent years, from the viewpoint of reducing the environmental load, it is desired to reuse waste generated during the manufacture of various industrial products. Therefore, it has been considered to produce a stretched film by forming a resin film using recycled materials regenerated from waste resin products and then stretching the film. However, when a resin film is formed using recycled materials, unevenness (specifically, uneven flow of the resin) occurs in the resin film, and as a result, the stretched film may not have the desired properties. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7096940 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned problems in the conventional art, and its main object is to provide a method for producing a stretched film that can suppress the occurrence of unevenness in a resin film even when the resin film is produced using recycled materials, and as a result, can produce a stretched film having desired properties. [Means for solving the problem]

[0005] [1] The method for producing a stretched film according to an embodiment of the present invention includes the steps of: preparing a virgin material containing a first resin and a recycled material containing a second resin and a mixed component; forming a long resin film from the virgin material and the recycled material, in which both ends in the width direction of the resin film are formed from the recycled material and a main part located between both ends in the width direction of the resin film is formed from the virgin material; cutting the resin film to separate it into a first end film including the ends in the width direction of the resin film and a film-formed film including the main part; and stretching the film-formed film in a direction crossing the longitudinal direction. The melt viscosity of the virgin material and the melt viscosity of the recycled material satisfy the following formula (1).

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[0006] According to an embodiment of the present invention, even when a resin film is produced using recycled materials, the occurrence of unevenness in the resin film can be suppressed, and a stretched film having desired properties can be produced. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic plan view of a resin film in a method for producing a stretched film according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic plan view of a stretched film obtained by stretching a film-formed film obtained from the resin film of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, in order to clarify the description, the width, thickness, shape, etc. of each part may be shown in a schematic manner compared to the embodiment, but it is merely an example and does not limit the interpretation of the present invention.

[0009] (Definition of terms and symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane retardation measured with light of wavelength λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light of wavelength 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx-ny)×d, where d(nm) is the thickness of the layer (film). (3)Angle When angles are referred to herein, unless otherwise specified, the angles include angles in both clockwise and counterclockwise directions.

[0010] A. Overview of the manufacturing process for stretched film FIG. 1 is a schematic plan view of a resin film in accordance with a method for producing a stretched film according to one embodiment of the present invention; FIG. 2 is a schematic plan view of a stretched film obtained by stretching a film-formed film obtained from the resin film of FIG.

[0011] A method for producing a stretched film according to an embodiment of the present invention includes a preparation step, a film-forming step, a first cutting step, and a stretching step, in this order. In the preparation step, a virgin material and a recycled material are prepared. The virgin material includes a first resin. The recycled material includes a second resin and a mixed component. The melt viscosity of the virgin material and the melt viscosity of the recycled material satisfy the following formula (1), and preferably satisfy the following formula (2).

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[0012] In one embodiment, the recycled material has a continuous phase comprised of the second resin; and a dispersed phase comprised of the entrained components. The maximum dimension of the dispersed phase is, for example, 1500 nm or less, preferably 1000 nm or less, more preferably 500 nm or less, even more preferably 350 nm or less, particularly preferably 250 nm or less, particularly preferably 200 nm or less, most preferably 100 nm or less, and, for example, 1 nm or more, preferably 10 nm or more, more preferably 30 nm or more, even more preferably 50 nm or more. If the maximum dimension of the dispersed phase is the above upper limit or less, it is possible to stably suppress the occurrence of unevenness in the resin film. If the maximum dimension of the dispersed phase is the above lower limit or more, it is possible to smoothly manufacture the recycled material. The maximum dimension of the dispersed phase can be measured, for example, by cross-sectional observation using a scanning electron microscope.

[0013] The contaminant components contained in the recycled material typically include foreign matter. The contaminant components may include a resin component different from the second resin in addition to the foreign matter. The foreign matter is a solid component different from the resin component.

[0014] The maximum dimension of the largest foreign object among the foreign objects contained in the mixed components is, for example, less than 3 mm, preferably less than 1 mm. If the maximum dimension of the largest foreign object is less than the above upper limit, the occurrence of unevenness in the resin film can be more stably suppressed. The maximum dimension of the foreign object can be measured, for example, by a particle counter.

[0015] In one embodiment, the foreign objects include a first foreign object having a maximum dimension of 500 μm or more and less than 1 mm; and a second foreign object having a maximum dimension of less than 500 μm. The foreign objects may include a third foreign object having a maximum dimension of more than 1 mm. The content of the first foreign matter in the foreign matter contained in the mixed components is, for example, 5 vol % or more, for example, 50 vol % or less, and preferably 40 vol % or less. The content of the second foreign matter in the foreign matter contained in the mixed components is, for example, 50% by volume or more, preferably 60% by volume or more, and is, for example, 95% by volume or less. If the content ratio of the first foreign matter and / or the second foreign matter is within the above range, the occurrence of unevenness in the resin film can be more stably suppressed.

[0016] Each step of the method for producing a stretched film will be described in detail below.

[0017] B. Preparation process In the preparation step, as described above, each of the virgin material and the recycled material is prepared.

[0018] B-1. Virgin materials The virgin material is a synthetic resin material that does not contain recycled resin material. The virgin material may be in the form of, for example, a pellet or a powder. In one embodiment, the virgin material is prepared as a virgin pellet. The following describes in detail the case where the virgin material is a virgin pellet.

[0019] The virgin pellets may have any suitable shape and size. The virgin pellets are typically cylindrical. The average maximum length of the virgin pellets is, for example, 1.0 mm or more and 5.0 mm or less. The mass of each virgin pellet is, for example, 5 mg or more and 25 mg or less.

[0020] Virgin pellets (virgin material) contain the first resin and do not substantially contain other components. The content of the first resin in the virgin pellets is, for example, 99.0 mass% or more, preferably 99.2 mass% or more, more preferably 99.5 mass% or more, and typically 100 mass% or less. That is, the content of other components in the virgin pellets is, for example, 1.0 mass% or less, preferably 0.8 mass% or less, more preferably 0.5 mass% or less, even more preferably 0.2 mass% or less, particularly preferably 0.09 mass% or less, particularly preferably 0.05 mass% or less, and typically 0 mass% or more.

[0021] The first resin is arbitrarily and appropriately selected depending on the application of the stretched film. Examples of the first resin include polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, (meth)acrylic resins, cellulose ester resins, cellulose resins, polyester resins, polyester carbonate resins, olefin resins, and polyurethane resins. Note that the (meth)acrylic resin refers to an acrylic resin and / or a methacrylic resin. These first resins may be used alone or in combination.

[0022] Among the first resins contained in the virgin pellets, polycarbonate (PC) resins, cycloolefin (COP) resins, (meth)acrylic resins, and polyester resins (typically, polyethylene terephthalate (PET)) are preferred, and PC resins are more preferred. When the first resin is such a resin material, it can stably impart desired properties to the stretched film (particularly the optical film).

[0023] An example of the PC resin is a PC resin containing a structural unit derived from a dihydroxy compound. Specific examples of dihydroxy compounds include 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-hydroxy-3-ethylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-propylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-sec-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-tert-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-cyclohexylphenyl)fluorene, 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, and 9,9-bis( 4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexyl phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, and 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene.In addition to the structural units derived from the above dihydroxy compounds, the PC resin may contain structural units derived from dihydroxy compounds such as isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecane dimethanol (TCDDM), and bisphenols.

[0024] Details of the above-mentioned PC-based resins are described, for example, in JP-A-2012-67300 and Japanese Patent No. 3325560. The descriptions in these patent documents are incorporated herein by reference.

[0025] The melt viscosity A of the virgin pellets (virgin material) is appropriately changed depending on the type of the first resin. The melt viscosity A of the virgin pellets is, for example, 300 Pa·s or more, preferably 500 Pa·s or more, more preferably 1000 Pa·s or more, and is, for example, 3000 Pa·s or less, preferably 2500 Pa·s or less. The melt viscosity of the pellets can be measured, for example, by a method according to JIS K 7199.

[0026] The virgin pellets may be prepared by any suitable method. The virgin pellets may be prepared by a strand cut method or a hot cut method. Details of the virgin pellet preparation method are described in, for example, JP 2013-181105 A. The description of the patent document is incorporated herein by reference.

[0027] B-2. Recycled materials The recycled material is a recycled resin material, which will be described in detail later. The recycled material may be in the form of, for example, a pellet or a powder. In one embodiment, the recycled material is prepared as recycled pellets. The following describes in detail the case where the recycled material is a recycled pellet.

[0028] The shape and size of the recycled pellets can be described in the same manner as the virgin pellets described above. The recycled pellets contain the second resin described above and the mixed components mixed into the second resin. In the recycled pellets, the second resin constitutes a continuous phase as a matrix resin, and the mixed components constitute a dispersed phase dispersed in particulate form in the continuous phase. The second resin contained in the recycled pellets (recycled material) and the first resin contained in the virgin pellets (virgin material) are typically the same.

[0029] The content of the second resin in the recycled pellets is, for example, 40.0 mass % or more, preferably 50.0 mass % or more, more preferably 70.0 mass % or more, and further preferably 90.0 mass % or more, for example, 99.1 mass % or less. The content of the contaminating components in the recycled pellets is, for example, 60.0% by mass or less, preferably 50.0% by mass or less, more preferably 30.0% by mass or less, and even more preferably 10.0% by mass or less. The lower limit of the content of the contaminating components in the recycled pellets is, for example, 0.3% by mass, for example, 0.5% by mass, or for example, 0.9% by mass. In the recycled pellets, the mass ratio of the mixed components to the second resin (mixed components / second resin) is, for example, 0.01 or more, and, for example, 1.5 or less, and preferably 1.0 or less. When the mixed components / second resin is within the above range, unevenness in the resin film can be stably reduced.

[0030] The contaminating components typically include the above-mentioned foreign matter. Examples of the foreign matter include amide-based foreign matter, fiber-based foreign matter, etc. The foreign matter may be mixed into the recycled pellets alone or in combination. The content of foreign matter in the mixed components is, for example, 1 volume % or more and 100 volume % or less, and, for example, 10 volume % or more and 50 volume % or less.

[0031] The contaminating components may include a resin component different from the second resin in addition to foreign matter. Examples of the resin component include the same resin components as the first resin described above. The contaminating components may include a single resin component or two or more resin components. In one embodiment, the resin component includes an olefin resin (typically, polyethylene). The content of the resin component in the mixed components is, for example, 0 volume % or more and 99 volume % or less, and, for example, 50 volume % or more and 90 volume % or less.

[0032] The air bubble content of the recycled pellets is, for example, 10% by volume or less, preferably 3% by volume or less, and more preferably 0% by volume. The air bubble content can be measured by observation and analysis using a microscope. If the air bubble content of the recycled pellets is equal to or less than the upper limit, the inclusion of air bubbles in the resin film can be suppressed.

[0033] The melt viscosity C of the recycled pellets (recycled material) is appropriately changed depending on the type of the second resin and the mixed components. The melt viscosity C of the recycled pellets is, for example, 200 Pa·s or more, preferably 350 Pa·s or more, and is, for example, 2800 Pa·s or less, preferably 2300 Pa·s or less.

[0034] The melt viscosity A of the virgin pellets and the melt viscosity C of the recycled pellets satisfy the above formula (1). The absolute value of the melt viscosity difference between the virgin pellets and the recycled pellets with respect to the melt viscosity A of the virgin pellets (|(CA) / A|) is 0 or more, preferably 0.05 or more, more preferably 0.08 or more, and is less than 0.65, preferably 0.60 or less, more preferably 0.55 or less, even more preferably 0.45 or less, particularly preferably 0.35 or less, particularly preferably 0.23 or less, and most preferably 0.20 or less. When |(CA) / A| is in the above range, unevenness in the resin film can be sufficiently reduced.

[0035] B-2-1. Preparation method of recycled pellets Recycled pellets may be prepared from regenerated resin materials by any suitable method. The recycled resin material is obtained by collecting discarded resin products or waste generated during the manufacture of resin products. Examples of the resin products include optical films such as retardation films; packaging materials made of thermoplastic resins such as polyethylene terephthalate (PET) and nylon. Among these resin products, optical films are preferred, and retardation films are more preferred. That is, the recycled pellets are preferably prepared from optical films (typically retardation films) and / or waste generated during the manufacture of optical films. As will be described in detail later, in the manufacturing method of the stretched film according to the embodiment of the present invention, the end film (first end film and / or second end film) generated as a by-product can be suitably used as a recycled resin material for the preparation of recycled pellets. The recycled resin material may be recycled multiple times. That is, the recycled pellets may be prepared from a resin product (typically an optical film) manufactured from a recycled resin material, and / or waste generated during the manufacture of the resin product.

[0036] The method for preparing the recycled pellets may be, for example, the same method as the method for preparing the virgin pellets described above. In one embodiment, the method for preparing the recycled pellets includes a step of melting the recycled resin material (melting step) and a step of extruding the molten recycled resin material (extrusion step).

[0037] The moisture content of the recycled resin material subjected to the melting step is, for example, 2.0% by mass or less, preferably less than 1.0% by mass, more preferably 0.9% by mass or less, and even more preferably 0.8% by mass or less. If the moisture content of the recycled resin material is equal to or less than the above upper limit (less than), it is possible to suppress the generation of air bubbles in the resin film prepared using the recycled pellets. The lower limit of the moisture content of the recycled resin material is typically 0.01% by mass or more. The moisture content of the recycled resin material can be measured, for example, by the Karl Fischer method.

[0038] Any appropriate method can be adopted to adjust the moisture content of the recycled resin material to the above range. For example, the recycled resin material may be stored in a moisture-proof bag.

[0039] The moisture-proof bag may have any suitable configuration. For example, the moisture-proof bag may be a packaging material with an inner bag to which aluminum is fused. The moisture-proof bag may have a moisture permeability of, for example, 10 g / m 2 24h or less, preferably 5g / m 2 24h or less, preferably 3g / m 2 The moisture permeability can be measured, for example, by the cup method. The storage time is, for example, 2 hours or more, preferably 12 hours or more, and, for example, 72 hours or less, preferably 36 hours or less. According to such a method, even if the recycled resin material is stored for the above-mentioned time, the moisture content of the recycled resin material can be stably maintained within the above-mentioned range. The storage temperature is, for example, from 0° C. to 30° C., and the storage humidity is, for example, from 0% RH (relative humidity) to 60% RH (relative humidity).

[0040] In the melting step, the recycled resin material is heated and melted. Typically, the recycled resin material is supplied into a cylinder in which a screw is housed, where it is heated and melted, and is kneaded by the screw.

[0041] The heating temperature and heating time are each set arbitrarily and appropriately according to the type of recycled resin material. The heating temperature is, for example, 80° C. or higher and 150° C. or lower. The heating time (residence time) is, for example, 6 hours or higher and 48 hours or lower.

[0042] The screw rotation speed is, for example, 5 rpm or more, preferably 10 rpm or more, more preferably 20 rpm or more, and even more preferably 40 rpm or more, and is, for example, 200 rpm or less, preferably 100 rpm or less, and more preferably 80 rpm or less. If the screw rotation speed is the above lower limit or more, the maximum dimension of the dispersed phase in the recycled pellets can be stably adjusted to the above upper limit or less. If the screw rotation speed is the above lower limit or more, the inclusion of air bubbles in the recycled pellets can be suppressed.

[0043] The screw length L relative to the screw diameter D (L / D) is, for example, 15 or more, preferably 20 or more, and for example, 60 or less, preferably 40 or less.

[0044] As a result, a recycled resin material in a molten state (hereinafter referred to as molten resin) is obtained. In one embodiment, the molten resin is passed through a filter before being subjected to the extrusion molding process, whereby coarse foreign matter contained in the molten resin can be removed from the molten resin.

[0045] The filter may have any suitable configuration, and examples of the filter include a screen mesh and a disk filter, and preferably a screen mesh. The opening of the screen mesh is, for example, 2.6 mm or less (8 mesh), preferably 2.0 mm or less (10 mesh), more preferably 0.60 mm or less (30 mesh), and even more preferably 0.15 mm or less (100 mesh), and is, for example, 0.034 mm or more (400 mesh), preferably 0.045 mm or more (300 mesh), and more preferably 0.060 mm or more (250 mesh). If the opening of the screen mesh is equal to or less than the upper limit, coarse foreign matter can be smoothly removed from the molten resin, and in particular, if the opening is less than 1.0 mm, coarse foreign matter having a maximum dimension exceeding 1 mm can be smoothly removed from the molten resin. If the opening of the screen mesh is equal to or more than the lower limit, the molten resin can be smoothly passed through.

[0046] In the extrusion process, the molten resin is discharged from a die and then cooled and solidified, thereby preparing recycled pellets. In the case of the strand cutting method for preparing recycled pellets, the molten resin is discharged from a die in the form of a thread and then cooled to obtain a strand made of recycled resin material, which is then cut to a predetermined size to obtain recycled pellets. When the method for preparing recycled pellets is the hot-cut method, the molten resin is extruded from a die in the form of a thread and immediately thereafter cut to obtain recycled pellets.

[0047] C. Film forming process 1, in the film-forming process, a long resin film 3 is formed from the above-mentioned virgin pellets and recycled pellets. More specifically, both ends 31 in the width direction of the resin film 3 are formed from the recycled pellets, and a main body portion 32 of the resin film 3 is formed from the virgin pellets, thereby forming one sheet of resin film 3. Details of the resin film production method are described in, for example, JP 2006-315275 A. The description of this patent document is incorporated herein by reference. More specifically, in the brittle resin film production method described in JP 2006-315275 A, virgin pellets are used as the brittle resin A and recycled pellets are used as the tough resin B, so that the resin film 3 can be produced.

[0048] The resin film 3 obtained in the film-forming process may have any appropriate configuration. As described above, the resin film 3 has a long shape. Any appropriate value may be adopted as the dimension in each direction of the resin film 3. The width of the resin film 3 (the dimension in the direction perpendicular to the long direction) is, for example, 500 mm or more, preferably 700 mm or more, and, for example, 2500 mm or less, preferably 2000 mm or less. The thickness of the resin film 3 is, for example, 40 μm or more, preferably 60 μm or more, and, for example, 200 μm or less, preferably 180 μm or less.

[0049] D. First cutting process In the first cutting step, both end portions 31 in the width direction of the resin film 3 are cut. In the illustrated example, two cutting lines 33 are formed on the resin film 3. The cutting lines 33 extend along the longitudinal direction of the resin film 3. The two cutting lines 33 are formed at a predetermined interval from each other in the width direction of the resin film 3, and each of the two cutting lines 33 is formed at a predetermined interval from an edge of the resin film 3 in the width direction.

[0050] As a result, the resin film 3 is separated into two first end films 6 including the widthwise ends 31 of the resin film 3, and the film-formed film 4 including the main body portion 32. Each of the two first end films 6 and the film-formed film 4 has an elongated shape.

[0051] The width of the first end film 6 is, when the width of the resin film 3 is 100%, for example, 1% or more, preferably 5% or more, more preferably 10% or more, and for example, 50% or less, preferably 30% or less. The width of the first end film 6 is, for example, 10 mm or more, preferably 50 mm or more, more preferably 100 mm or more, and for example, 1000 mm or less, preferably 600 mm or less. When the width of the first end film is the above lower limit or more, the first end film can sufficiently contain a portion derived from the recycled pellets. When the width of the end film is the above upper limit or less, the yield of the stretched film can be improved.

[0052] The first end film 6 may be recovered by any appropriate method. The recovered first end film 6 can be suitably used as a recycled resin material in the above-mentioned method for preparing recycled pellets.

[0053] E. Stretching process As shown in Fig. 2, in the stretching step, a long film-formed film 4 is stretched in a direction intersecting the long direction. Any appropriate stretching method can be adopted. Various stretching methods such as free-end stretching and fixed-end stretching can be used alone, or simultaneously or sequentially. Among the stretching methods, fixed-end uniaxial stretching is preferable.

[0054] Fixed-end uniaxial stretching is typically performed by a stretching device equipped with clips capable of gripping the widthwise ends of the film-formed film 4. The stretching device is typically a tenter stretching device. The stretching device stretches the film-formed film 4 in a direction intersecting with the longitudinal direction while each of the widthwise ends of the film-formed film 4 is gripped (typically clamped) by clips. The stretching direction may be a direction substantially perpendicular to the longitudinal direction of the film-formed film 4 (for example, 90°±1° with respect to the longitudinal direction), or may be a direction intersecting both the longitudinal direction and the width direction of the film-formed film 4.

[0055] Details of the stretching step are described, for example, in Japanese Patent No. 7096940, JP 2004-226686 A, and WO 2007 / 111313, the disclosures of which are incorporated herein by reference.

[0056] This produces a long stretched film 5 as shown in Fig. 2. The stretching ratio in the width direction in the stretching step (width of stretched film / width of formed film) is, for example, 1.1 or more, preferably 1.5 or more, and for example, 6.0 or less, preferably 4.0 or less.

[0057] The stretched film 5 typically has a slow axis in the stretching direction and is configured as a retardation film. The refractive index of the stretched film 5 satisfies the relationship nx>ny.

[0058] In one embodiment, the stretched film 5 functions as a λ / 4 plate. When the product film functions as a λ / 4 plate, the in-plane retardation Re(550) of the stretched film 5 is, for example, 100 nm to 180 nm, and preferably 135 nm to 155 nm. In another embodiment, the stretched film 5 functions as a λ / 2 plate. When the stretched film functions as a λ / 2 plate, the in-plane retardation Re(550) of the stretched film is, for example, 230 nm to 310 nm, and preferably 250 nm to 290 nm.

[0059] The wavelength dependency of the stretched film 5 is not particularly limited. The stretched film 5 preferably exhibits wavelength dependency of reverse dispersion. The Re(450) / Re(550) of the stretched film 5 is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.95. The Re(550) / Re(650) of the stretched film 5 is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.97.

[0060] The absolute value of the photoelastic coefficient of the stretched film 5 is, for example, 2×10 -12 (m 2 / N)~100×10 -12 (m 2 / N), preferably 5×10 -12 (m 2 / N)~50×10 -12 (m 2 / N).

[0061] F.Second cutting process In one embodiment, the production of the stretched film further includes a second cutting step, in which both ends of the stretched film 5 in the width direction are cut.

[0062] In the illustrated example, two cutting lines 55 are formed in the stretched film 5. The cutting lines 55 extend along the longitudinal direction of the stretched film 5. The two cutting lines 55 are formed at a predetermined interval from each other in the width direction of the stretched film 5, and each of the two cutting lines 55 is formed at a predetermined interval from an edge of the stretched film 5 in the width direction.

[0063] When fixed-end uniaxial stretching is performed in the stretching step, clip marks 51 may be formed on both widthwise ends of the stretched film 5. The clip marks 51 are harder and more brittle than the portions of the stretched film 5 other than the grip marks 3.

[0064] The slow axis of the stretched film 5 may be misaligned in the width direction. More specifically, the direction of the slow axis of the stretched film 5 is likely to deviate from the desired angle at the width direction end. Typically, the axis misalignment is not substantially manifested at the width direction center of the stretched film 5, and becomes larger toward the width direction end. In the illustrated example of the stretched film 5, the slow axis is substantially parallel to the stretching direction at the width direction center (for example, the axis misalignment is less than 0°±1°). Furthermore, at the width direction end of the stretched film 5, the slow axis may intersect with the stretching direction (for example, the axis misalignment is 1° to 3°).

[0065] Therefore, by carrying out the second cutting step, it is possible to remove the grip marks 51 of the clip and / or the portion of the stretched film where the axial misalignment is relatively large from the stretched film 5. In addition, two second end films 7 corresponding to both ends of the stretched film 5 in the width direction are obtained from the stretched film 5.

[0066] The second end film 7 in the illustrated example includes gripping marks 51 of the clip. Furthermore, the stretched film 2 from which the two second end films 7 have been cut is configured as a product film 8. That is, in the second cutting step, the stretched film 5 is typically separated into the two second end films 7 and the product film 8. The product film 8 is typically configured as the above-mentioned retardation film.

[0067] The width of the second end film 7 is, when the width of the stretched film 5 is 100%, for example, 0.5% or more, preferably 1.0% or more, more preferably 5.0% or more, and even more preferably 10.0% or more, and for example, 30% or less, preferably 25% or less, and more preferably 20% or less. The width of the second end film 7 is, for example, 10 mm or more, preferably 20 mm or more, more preferably 100 mm or more, and even more preferably 200 mm or more, and for example, 600 mm or less, preferably 500 mm or less, and more preferably 300 mm or less. When the width of the second end film is equal to or greater than the lower limit, the second end film can stably include the entire gripping mark of the clip, and the portion of the stretched film where the axial misalignment is relatively large can be included in the second end film. As a result, the gripping mark of the clip can be prevented from remaining on the product film, and the axial misalignment of the product film can be reduced. When the width of the second end film is equal to or less than the upper limit, the yield of the product film can be improved.

[0068] The second end film 7 may be recovered by any suitable method. The recovered second end film 7 may be suitably used as a recycled resin material in the above-mentioned method for preparing recycled pellets. In other words, the production of the stretched film may further include a step of preparing recycled pellets from the recycled resin material including the first end film 6 and / or the second end film 7. EXAMPLES

[0069] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement methods for each property are as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on mass. The measurement methods for each property in the examples and comparative examples are as follows.

[0070] (1) Measurement of melt viscosity of virgin pellets and recycled pellets The melt viscosity of the virgin pellets and recycled pellets used in the examples and comparative examples was measured at a shear rate of 100 sec in accordance with JIS K 7199. -1 The measurements were performed at a temperature of 24° C. The results are shown in Tables 1 to 3.

[0071] (2) Measurement of the maximum size of the dispersed phase in recycled pellets The maximum size of the dispersed phase in the recycled pellets used in the examples and comparative examples was measured by observation with a scanning electron microscope. The results are shown in Tables 1 to 3.

[0072] (3) Measurement of the maximum size of foreign matter contained in the recycled pellets and the content ratio of each component in the foreign matter The maximum dimensions of foreign matter in the recycled pellets used in the examples and comparative examples were measured by a particle counter. The foreign matter included a first foreign matter having a maximum dimension x of 500 μm or more and less than 1 mm, and / or a second foreign matter having a maximum dimension x of less than 500 μm. The foreign matter in Example 14 included a third foreign matter having a maximum dimension x of 1 mm or more, in addition to the first foreign matter and the second foreign matter. The content ratio (volume %) of each of the first foreign matter, the second foreign matter, and the third foreign matter was calculated by observation and analysis using an optical microscope. The results are shown in Tables 1 to 3.

[0073] (4) Moisture content of edge film In the examples and comparative examples, the moisture content of the end film (recycled resin material) immediately before being subjected to the manufacturing process for recycled pellets was measured by the Karl Fischer method. The results are shown in Tables 1 to 3.

[0074] (5) Unevenness in resin film The resin films prepared in the examples and comparative examples were checked for unevenness (unevenness in resin flow) by visually observing the degree of distortion when viewed through the film, and were evaluated according to the following criteria. The results are shown in Tables 1 to 3. 5: There is absolutely no distortion when viewed through transmission. 4: There is some distortion when viewed through a transparent lens. 3: There is distortion when viewed through transmission. 2: Severe distortion when viewed through transmission (acceptable for practical purposes). 1: When viewed through a transparent medium, it is not possible to see through to the other side (unacceptable for practical purposes).

[0075] (6) Air bubbles in the resin film The presence or absence of air bubbles in the resin films prepared in the examples and comparative examples was confirmed using an optical microscope. The results are shown in Tables 1 to 3.

[0076] <<Preparation of edge film>> <Preparation Examples 1 to 6> In the same manner as in Production Example 9 of JP 2022-150732 A, a resin film composed of a PC resin was prepared, and the resin film was stretched to prepare a stretched film composed of a PC resin. The thickness of the stretched film was 48 μm. Next, each of the two end portions in the width direction of the stretched film was cut by a slitter (cutting device) to obtain two end films (recycled once). Each of the two end films had a width of 250 mm. Next, the obtained end film was washed with water, and then dried under conditions of 100° C. and 10 minutes (number of washings: 1 time). Next, the end film was placed in a moisture-proof bag (product name: moisture-proof packaging bag one-side sewing machine, moisture-proof type, manufactured by Yamaguchi Packaging Industry Co., Ltd.) under the environment shown in Table 1 or 3 and stored for 24 hours.

[0077] <Preparation Example 7> An end film was prepared and stored in the same manner as in Preparation Example 1, except that the moisture-proof bag was changed to a non-moisture-proof bag (product name: Inner Bag Aluminum Bag, manufactured by Yamaguchi Packaging Industry Co., Ltd.).

[0078] <Preparation Examples 8 to 13> Using the end film obtained in Preparation Example 1, recycled pellets were produced in the same manner as in Example 1 described later (preparation step), a resin film was produced from the virgin pellets and the recycled pellets (film production step), the resin film was cut to separate it into a first end film and a film-formed film (first cutting step), the film-formed film was then stretched (stretching step), and the obtained stretched film was cut to separate it into a second end film and a product film (second cutting step). Next, the preparation step, film-formation step, first cutting step, stretching step, and second cutting step were repeated using the obtained second end film until the recycling number shown in Table 1 or 3 was reached. In this way, an end film (second end film) with the recycling number shown in Table 1 or 3 was prepared. The obtained end film was then stored in the same manner as in Preparation Example 1.

[0079] <Preparation Examples 14-16> In the same manner as in Production Example 9 of JP 2022-150732 A, a resin film composed of a PC resin was prepared, and the resin film was stretched to prepare a stretched film composed of a PC resin. The thickness of the stretched film was 48 μm. Next, a polyethylene (PE) film (thickness: 48 μm) was attached as a protective film to the surface of the stretched film via an acrylic adhesive layer. Then, both ends of the laminated film of the stretched film and the protective film in the width direction were cut by a slitter (cutting device) to obtain two end films (recycled number: 1 time). The width of each of the two end films was 250 mm. Next, the obtained end film was washed with water. After that, the end film was dried under the conditions of 100° C. and 10 minutes (number of washings: 1 time). Then, the end film was stored in the same manner as in Preparation Example 1.

[0080] <Preparation Example 17> An end film was prepared and stored in the same manner as in Preparation Example 14, except that the thickness of the PE film used as the protective film was changed to 96 μm.

[0081] <Preparation Example 18> An edge film was prepared and stored in the same manner as in Preparation Example 1, except that the edge film was washed and dried five times.

[0082] <Preparation Examples 19 and 20> Except for changing the resin film made of PC resin to a resin film made of PET (manufactured by Toray Industries, product number "50U48"), an end film was prepared and stored in the same manner as in Preparation Example 1. The thickness of the stretched film obtained by stretching the resin film was 50 μm.

[0083] <Preparation Example 21> Except for using the end film obtained in Preparation Example 19 instead of the end film obtained in Preparation Example 1, the preparation step, film-forming step, first cutting step, stretching step, and second cutting step were repeated in the same manner as Preparation Example 8 until the recycling number shown in Table 2 was reached. In this way, the end film (second end film) with the recycling number shown in Table 2 was prepared. The obtained end film was then stored in the same manner as Preparation Example 1.

[0084] <Preparation Example 22> Except for changing the resin film made of PC resin to a resin film made of PET (manufactured by Toray Industries, product number "50U48"), an end film containing a PE film was prepared and stored in the same manner as in Preparation Example 14. The thickness of the stretched film obtained by stretching the resin film was 50 μm, and the thickness of the PE film was 50 μm.

[0085] <Preparation Examples 23 and 24> Except for changing the resin film made of PC resin to a resin film made of acrylic resin (manufactured by Kaneka Corporation, product name "HTX-Z"), an end film was prepared and stored in the same manner as in Preparation Example 1. The thickness of the stretched film obtained by stretching the resin film was 40 μm.

[0086] <Preparation Example 25> Except for using the end film obtained in Preparation Example 23 instead of the end film obtained in Preparation Example 1, the preparation step, film-forming step, first cutting step, stretching step, and second cutting step were repeated in the same manner as Preparation Example 8 until the number of recycling steps shown in Table 2 was reached. In this way, end films (second end films) with the number of recycling steps shown in Table 2 were prepared. The obtained end films were then stored in the same manner as Preparation Example 1.

[0087] <Preparation Example 26> Except for changing the resin film made of PC resin to a resin film made of acrylic resin (manufactured by Kaneka Corporation, product name "HTX-Z"), an end film containing a PE film was prepared and stored in the same manner as in Preparation Example 14. The thickness of the stretched film obtained by stretching the resin film was 80 μm, and the thickness of the PE film as a protective film was 80 μm.

[0088] <Preparation Examples 27 and 28> Except for changing the resin film made of PC resin to a resin film made of COP resin (manufactured by Zeon Corporation, product number "ZF16"), an end film was prepared and stored in the same manner as in Preparation Example 1. The thickness of the stretched film obtained by stretching the resin film was 40 μm.

[0089] <Preparation Example 29> Except for using the end film obtained in Preparation Example 27 instead of the end film obtained in Preparation Example 1, the preparation step, film-forming step, first cutting step, stretching step, and second cutting step were repeated in the same manner as Preparation Example 8 until the recycling number shown in Table 2 was reached. In this way, the end film (second end film) with the recycling number shown in Table 2 was prepared. The obtained end film was then stored in the same manner as Preparation Example 1.

[0090] <Preparation Example 30> Except for changing the resin film made of PC resin to a resin film made of COP resin (manufactured by Zeon Corporation, product number "ZF16"), an end film containing a PE film was prepared and stored in the same manner as in Preparation Example 14. The thickness of the stretched film obtained by stretching the resin film was 40 μm, and the thickness of the PE film as a protective film was 40 μm.

[0091] [Examples 1 to 26, Comparative Examples 1 to 7] The end film after storage obtained in each preparation example was supplied as a recycled resin material to a pellet manufacturing device (strand cut type) equipped with a filter shown in Tables 1 to 3. In the pellet manufacturing device, the end film was heated to 270°C to melt and passed through the filter shown in Tables 1 to 3. Thereafter, recycled pellets were manufactured by extrusion molding under the extrusion conditions (screw rotation speed, compression ratio and effective length) shown in Tables 1 to 3. The mass ratio of the mixed component / second resin in the recycled pellets is shown in Tables 1 to 3.

[0092] Separately, virgin pellets were produced by melt extrusion in accordance with the method described in JP 2013-181105 A. The virgin pellets contained the first resins shown in Tables 1 to 3. The content of the first resin in the virgin pellets was 100% by mass.

[0093] Next, a resin film was formed from the virgin pellets and the recycled pellets. More specifically, in accordance with the examples of JP 2006-315275 A, both ends in the width direction of the resin film were formed from the recycled pellets, and the main body portion located between both ends in the width direction of the resin film was formed from the virgin pellets. The width of the resin film was 800 mm. The thickness of the resin film was 200 μm.

[0094] The resin film was then cut by a slitter (cutting device) into a first end film including the end in the width direction of the resin film and a film-formed film including the main body portion. The width of each of the two first end films was 60 mm (7.5% when the width of the resin film was 100%).

[0095] Next, the film-formed film was stretched in the width direction in accordance with Production Example 9 of JP 2022-150732 A. Thus, a stretched film was obtained. The stretching ratio was 3.0 times. The width of the stretched film was 2000 mm.

[0096] The stretched film was then cut by a slitter (cutting device) to separate it into two second end films and a product film. The width of each of the two second end films was 250 mm (12.5% ​​of the width of the stretched film, which is 100%). The width of the product film was 1500 mm.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

[0100] [evaluation] As is clear from Tables 1 to 3, when the melt viscosity of the virgin pellets and the melt viscosity of the recycled pellets satisfy the above formula (1), it is possible to suppress unevenness in the resin film. Furthermore, when the maximum dimension of the dispersed phase in the recycled pellets is 500 μm or less and / or the maximum dimension of the foreign matter is less than 1 mm, it is possible to further suppress unevenness in the resin film. [Industrial Applicability]

[0101] The method for producing a stretched film of the present invention is used for producing a stretched film that can be used for various industrial products, and is particularly suitable for producing an optical film (specifically, a retardation film). [Explanation of symbols]

[0102] 3. Resin film 31 End of resin film in width direction 32 Main body part 4. Film-forming film 5. Stretched film 6 First edge film 7 Second end film

Claims

1. Providing a virgin material comprising a first resin and a recycled material comprising a second resin and contaminant components; a step of forming a long resin film from the virgin material and the recycled material, wherein both ends in a width direction of the resin film are formed from the recycled material, and a main body portion located between both ends in the width direction of the resin film is formed from the virgin material; cutting the resin film to separate it into a first end film including an end portion in a width direction of the resin film and a film-forming film including the main body portion; Stretching the film in a direction intersecting the longitudinal direction; A method for producing a stretched film, wherein the melt viscosity of the virgin material and the melt viscosity of the recycled material satisfy the following formula (1): [0010] (In formula (1), A represents the melt viscosity [Pa·s] of the virgin material, and C represents the melt viscosity [Pa·s] of the recycled material.)

2. The method for producing a stretched film according to claim 1, wherein the melt viscosity of the virgin material and the melt viscosity of the recycled material satisfy the following formula (2): [0025] (In formula (2), A represents the melt viscosity [Pa·s] of the virgin material, and C represents the melt viscosity [Pa·s] of the recycled material.)

3. the recycled material has a continuous phase comprised of the second resin and a dispersed phase comprised of the contaminant components; The method for producing a stretched film according to claim 1 or 2, wherein the maximum dimension of the dispersed phase is 500 nm or less.

4. The method for producing a stretched film according to claim 3, wherein the maximum dimension of the dispersed phase is from 10 nm to 200 nm.

5. The contaminating components include foreign matter other than the resin component, The method for producing a stretched film according to claim 1 or 2, wherein the maximum dimension of the largest foreign particle among the foreign particles contained in the mixed components is less than 1 mm.

6. The foreign matter includes a first foreign matter having a maximum dimension of 500 μm or more and less than 1 mm, and a second foreign matter having a maximum dimension of less than 500 μm, The method for producing a stretched film according to claim 5 , wherein the content of the first foreign matter is 5 volume % or more and 50 volume % or less, and the content of the second foreign matter is 50 volume % or more and 95 volume % or less.

7. The method for producing a stretched film according to claim 3 , further comprising a step of cutting each of both widthwise end portions of the stretched film to obtain second end films.

8. The method for producing a stretched film according to claim 7, further comprising the step of preparing a recycled material from a recycled resin material comprising the first end film and / or the second end film.

9. The method for producing a stretched film according to claim 8 , wherein the recycled resin material has a moisture content of less than 1.0% by mass.

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